Effects of leptin therapy on hypothalamic structure and function in congenital lipodystrophy

Congenital lipodystrophy is a rare disorder, characterized by the absence of
adipocytes, resulting in accumulation of triglycerides in the liver and
muscles. Severe steatosis of the liver develops in childhood followed by
insulin resistance, diabetes and severe hypertriglyceridemia. Treatment with
antidiabetic drugs, insulin and triglyceride-lowering drugs is usually
insufficient to control this metabolic disorder. Due to the absence of
adipocytes plasma leptin levels are low. Supplementation with leptin may
effectively improve the diabetes and hypertriglyceridemia, by reducing the
accumulation and production of triglycerides by the liver. Liver fat content
and liver size may subside significantly.
Leptin has several specific effects:
1. Stimulates T3,T4, IGF-1, reproductive hormones and fatty acid oxidation in
muscle cells.
2. Inhibits fatty acid synthesis, triglyceride storage and VLDL production in
the liver
3. Inhibits bone formation via ventromed neurons of hypothalamus, autonomous CS
and Beta-adrenergic receptors of the osteoblast.
In leptin deficiency bone density may therefore be increased.
4. Stimulates angiogenesis in adipose tissues
5. Reduces insuline resistance
Leptin suppresses apetite through activation of pro-opiomelanocortine (POMC)
neurons. In turn these neurons activate the melanocortin-4 receptor resulting
in activation of α-melanocyte stimulating hormon.[2] Energy expenditure will
increase. Agouti-related protein (AgRP) and neuropeptide-Y (NPY)-producing
cells of the arcuate nucleus is inhibited by leptine. The inhibitory effects of
AgRP and NPY on POMC neurons and α-MSH are impaired by leptin. Without leptin
the NPY/AgRP systeem is active and suppresses POMC neurons resulting in
stimulation of the appetite.
Moreover stimulation by leptin of the histamin H1-receptor in the hypothalamus
increases sympathic activity, which stimulates energy expenditure.

We hypothesize that longstanding leptin deficiency may alter hypothalamic
function and structure. At present new MRI technology is available to study
function and structure of the hypothalamus.
Recently it was found with functional MRI (3 Tesla) that hypothalamic activity
in patients with diabetes is reduced after an oral glucose load in comparison
with healthy controls.







Aim of the study
In addition to the aims of the standard protocol.

To study:
1. hypothalamic structure before and during leptin therapy
2. hypothalamic function before and during leptin therapy

Aim of the study
In addition to the aims of the compassionate use protocol.

To study:
1. hypothalamic structure before and during leptin therapy
2. hypothalamic function before and during leptin therapy

fMRI (3 Tesla): hypothalamic function, before and during standard oral glucose
tolerance test

at visit 1,2 and 5 (day 1, week 1 and month 3)

MRI (7Tesla): hypothalamic structure at visit 1 and visit 5 (day 7 and month 3)


Oral glucose tolerance test:

Subjects ingest a glucose solution through an oral tube, 7 min. after the start
of the fMRI scan. The glucose solution consists of 75 gram of glucose dissolved
in 296 ml water, which is similar to the normal standardized OGTT.
fMRI is a non-invasive method, which detects transient haemodynamic changes in
the brain, using blood oxygen level dependent (BOLD) signal differences in
response to external or internal stimuli. BOLD signal differences (contrasts)
measured with T2* weighted fMRI imaging sequences are dependent on local and
global oxygen content, blood volume, perfusion and/or tissue metabolism. These
factors potentially influence the oxy-to-deoxyhaemoglobin ratio, and hence
result in variation in the fMRI signal. We will employ this technique to
examine hypothalamic neuronal activity in response to glucose ingestion at all
three time points.
The hypothalamic BOLD signal will be recorded for 43 minutes, starting from 7
minutes before ingestion of glucose solution. Depending on the time subjects
need for ingestion, the BOLD signal will be measured for approximately 27-32
after ingestion. fMRI will be performed on a 3.0 Tesla scanner (Philips
Achieva, Philips Medical Systems, Best, The Netherlands).
Scanparameters:T2*-weighted echo-planar imaging (EPI) sequence with TR/TE/flip
angle=120ms/ 30 ms/ 30°, image matrix = 256 x 231, field of view = 208 x 208
mm, slice thickness =14mm. midsagittal slice. A T1-weighted anatomical scan
will be made of the same slice (repetition time = 550 ms, echo time = 10 ms,
field of view = 208 x 208 mm).

The MRS technique is noninvasive involving no catheterizations or introduction
of exogenous tracers. Numerous human subjects have undergone magnetic resonance
studies without apparent harmful consequences. Radiofrequency power levels and
gradient switching times used in these studies are within the FDA approved
ranges. Contraindications to MRI studies are:
1. presence of a pacemaker or a subcutaneous defibrillator;
2. presence of metal clips in cerebral blood vessels, metal splinters in eye or
non-removable piercings,
3. presence of a non-removable hearing aid, a neurostimulator or a
hydrocephalus pump,
4. presence of denture kept in place by a magnet or metal wire behind the teeth
(crowns, dental fillings and removable braces are allowed).
5. claustrophobia is a relative contraindication. If individuals become
claustrophobic while inside the device, the study will be terminated
immediately at the subject's request.